Desmopressin, also known as dDAVP, is a nonapeptide and the therapeutically active ingredient (as its acetate salt) in the pharmaceutical product Minirin®, which is marketed inter alia as a nasal spray and a tablet formulation. Desmopressin is primarily used in the treatment of primary nocturnal enuresis, i.e. bedwetting, in children, but it is approved also for the treatment of nocturia and diabetes insipidus. The first market introduction of the tablet formulation was in Sweden in 1987. The composition of the marketed tablet form of desmopressin has remained the same to the present date.
The tablet form of desmopressin was first disclosed as set forth in the U.S. Pat. No. 5,047,398. The subsequently issued marketing authorisations relate to a tablet where i.a. the mannitol, talc and cellulose components exemplified in U.S. Pat. No. 5,047,398 are replaced with potato starch. In addition to desmopressin acetate and potato starch, the present tablet components are lactose, polyvinylpyrrolidone (PVP) and magnesium stearate that together form a homogeneous tablet compressed from a granulate. As a mixture of water and ethanol is used as granulation liquid in the granulate preparation, the resulting tablet also contains minor residues of those two solvents, typically 5-6% of water and 0.1% of ethanol (percentage by weight). Complete removal of residual solvents is neither required nor practical, as conditions for complete drying of solid dosage forms tend to be either too costly in industrial scale or potentially thermally damaging to the desmopressin.
A Minirin® tablet has previously been marketed contained in a blister pack comprising polyvinyl chloride (PVC) blisters coated with PVDC (polyvinylidene chloride). An aluminium foil lid provided with a heat seal lacquer was utilised. The blister pack product was withdrawn from the market in 2002 due to a consistent problem with degradation of the desmopressin acetate during long term storage.
The advantages of blister packs compared to a spray or tablets in a bottle are well known. They involve mainly the treating physician's flexibility in selecting a particular number of dosage units and the appearance of the blisters as a practical reminder to the patient of whether a dosage unit has been taken or not. More general guidance on blister packs available for pharmaceutical use is provided in “Pharmaceutics—The science of dosage form design”; Ed. M. E. Aulton, Churchill Livingstone, Edinburgh, London, Melbourne and New York, 1988.
There exists a need to provide a blister pack comprising desmopressin that does not suffer from a storage stability problem.
The U.S. Pat. No. 5,763,405 discloses a solid dosage form of desmopressin. It has an enteric coating adapted for providing desmopressin release in the small intestine, and the drug is admixed with a carrier comprising a buffering agent that buffers at a pH from about 2 to about 6. U.S. Pat. No. 5,763,405 discloses the objective of increasing the desmopressin bioavailability by controlling the gastrointestinal release and ensuing enzymatic degradation of desmopressin.